In modern manufacturing facilities for processing workpieces such as semiconductor wafers, flatpanel display substrates, and lithography masks, with a lack of in-situ workpiece measurements, critical chamber components for workpiece processing tools must be closely monitored during processing. Typically, each of these components is regularly scheduled for preventive maintenance with the goal of within-specification performance.
For the application of manufacturing semiconductor devices from semiconductor wafers, critical dimensions (CDs) and wafer yields are frequently measured during regular tool operation; any deviations are carefully analyzed by experienced fab personnel to identify faulty process chamber components. This troubleshooting process is time, labor, and material intensive.
Plasma environments can be extremely harsh on sensitive metrology equipment. The combination of high radio frequency (RF) powers and corrosive chemistries attack any materials placed into these environments. This is widely demonstrated by the normal consumption of in-chamber materials, deemed “consumables” for this reason. Nevertheless, as the semiconductor industry calls for smaller critical dimensions, tighter plasma process control solutions are required—in-situ plasma monitoring now becomes a necessity. In particular, extreme applications such as high aspect ratio dielectric applications and sub-90 nm polysilicon gates require the ability to accurately measure small signals related to the etching process despite the noise inherent in this environment.
The performance of etch processes during semiconductor manufacturing is strongly affected by various interacting mechanisms including chemical reactions, reactive ion etching, thin film deposition, and mask erosion. All of these processes are very sensitive to temperature, allowing temperature to be used as a tool for the detection of many issues within the plasma chamber and on the wafer. In particular, within-wafer and run-to-run variations in temperature can often be directly linked to failures in critical etch chamber components such as the electrostatic chuck (ESC), radio-frequency generators, and mass-flow controllers. Measurement of the thermal profile at the surface of the wafer provides information about the reactions on the wafer's surface (i.e. the process zone).
There is a need for improved methods and apparatus for monitoring, optimizing, detecting failures, and/or assessing the operating performance of components and sub-components of process tools for processing workpieces. Examples of applications that are of particular importance are applications such processing semiconductor wafers, processing flat panel displays, and processing lithography masks. There is also a need for methods and apparatuses suitable for characterizing processes and process tools.